Does the glowplug light ALWAYS come on?

[winmutt]

I have noticed that mine does not always come on. In the morning after sitting all night as well as on errands. I believe my euro has the pecil type not loop type plugs.

[rrgrassi]

My '82 300D GP dash light always comes on, whether hot or cold starting. I also have the pencil type GP's.

[sailor15015]

Pencil plugs here, too. I believe it should always come on. Maybe you have a plug that's on its way out. I had three that were out, however, and my light still came on (resistance read open and wounldn't light off.)

[barry123400]

My 77 300d does not always indicate. I usually just turn the key back and try again. Usually works. I will try starting it one day with the light out when I initially turn the key on after 20 seconds or so to see if the relays primary function is still there. Just never bothered yet. Also remember another car not mercedes that had this symptom. Never bothered to resolve it either. But if really interested I would monitor the glow plug voltage to see if they were on just after I turned the key on with the light out. Could even be a loose bulb or marginal wiring connection but most likely the relay or perhaps the keyswitch on the 1977. The pencil glowplug type are more prone to have the number one glow plug cause difficulty in this area but not the series plugs. I thought I read somewhere that the pencil type glow relay reads the resistance of the number one plug for operational refference but I might be wrong. Anyways if one were to swap the first two glowplug positions it would clear it or condem it as the cause.

[Maroon 300D]

Mine does not always light up but when I try and start it, it seems to work normally. Sometimes the light doesn't come on right away when the key reaches the '2' position but does light up eventually, but only for a second.

Before I just finally tried to start it I would wait a minute and try again, and the light would always come on. I've tested my plugs for resistance and they seem fine...I just replaced them about 5 months ago so I suspect they are indeed OK. The car starts fine.

I've kind of figured it's a loose wire or something. I'm actually glad to read this happens to others, too.

I would say that at least 95 times out of 100 it just comes on normally.

[winmutt]

I'm guessing that winter will tell the truth.

[Johnhef]

if its not coming on either you've got a plug out or your relay is malfunctioning. chances are its a plug.

[bbeardb]

Mine only comes on for about a second EVERY time, no matter the temperature. All my plugs test fine and the car always starts fine. I just use the seat belt buzzer as a timer. In the cold of winter, I just wait to hear the relay click off. No problems at all.

Still, wouldn't mind if the light worked though...

[iNeon]

Why hasn't anyone mentioned that the bulb itself will burn out at some point?

Check the light bulb first

[winmutt]

Its an intermittent issue.

[sodapop6620]

The light always comes on in my 84 Euro.

[taygan]

I've got the old salt shaker, on that one it has to come on, but on my old VWs the relay controls the light separately from the glow plugs, so it may be possible just for the light not to work if the relay is going bad, or has loose connections to it.

Mine always comes on regardless of engine temp. I've owned two vw rabbits, and there was some kind of temp sensor which cut off the glow plug circuit when the engine was warm=no glow plug light. Seems like this system would be beneficial for longer glow plug life since the plugs will not operate as much. I did buy a set of wratchet wrenchs at a truckload tool sale for under $20, so at least when it is time to replace the glow plugs it will take much less time.

[running-snail]

This just started on mine. Always lights the 2nd time (turn the key off, then back on again). Looking for answers???

[Johnhef]

you've got a dead plug.